Switch unit especially toggle switch unit

ABSTRACT

A SWITCH UNIT IN WHICH A PAIR OF CONTACT MEANS MOVABLE BETWEEN AN OPEN AND A CLOSED POSITION ARE ARRANGED IN A PAIR OF CHAMBERS FORMED IN A SOCKET, IN WHICH AN OPERATING MEMBER COOPERATES WITH ONE OF SAID CONTACT MEANS TO MOVE THE SAME BETWEEN THE OPEN AND THE CLOSED POSITION AND WITH THE OTHER CONTACT MEANS TO MOVE THE LATTER TO THE CLOSED POSITION, AND IN WHICH HEAT-RESPONSIVE MEANS COOPERATE WITH THE OTHER OF THE CONTACT MEANS TO MOVE THE LATTER FROM THE CLOSED TO THE OPEN POSITION WHEN OVERLOAD OCCURS IN THE CIRCUIT CONNECTED TO THE CONTACT MEANS. THE UNIT MAY ALSO INCLUDE A SIGNAL LAMP MOUNTED ON THE OPERATING MEMBER AND THE SIGNAL LAMP MAY BE CONNECTED TO THE CONTACT MEANS IN SUCH A MANNER THAT THE LAMP IS ENERGIZED EITHER WHEN THE OTHER CONTACT MEANS ARE IN THE OPEN OR WHEN THEY ARE IN THE CLOSED POSITION.

Feb. 9, 1971 5 B 3,562,689

SWITCH UNIT, ESPECIALLY TOGGLE SWITCH UNIT Filed April 23, 1959 2 Sheets-Sheet 1 INVENTOP g par un [54ft a, m. M1 M44 j A fr 7/ 7 Feb. 9, 1971 5 BAR SWITCH UNIT, ESPECIALLY TOGGLE SWITCH UNIT Filed April 23, 1969 2 Sheets-Sheet 2 Q A 2 4 3 R W 9 l, 3 T m 6 4 E e 0 I 6 V H /u a 7 M m n M 4 5 6 n0 5 v 6 5 W c o 1 i F 3 P W 5 G W 8 I 5 l 4 mm D B 5 A PH" M w 3 H M J x W I l 0 DJ E n Q m 2 Afi v l\n*u 70 M F mm P U. nk): IYZMM L -W// 5 4 fl w M y & 6 6 B b B United States Patent Ofiice 3,562,689 Patented Feb. 9, 1971 7 3,562,689 SWITCH UNIT, ESPECIALLY TOGGLE SWITCH UNIT Siegfried Bar, Schalksmuhle, Westphalia, Germany, as-

signor to Bar Elektrowerke GmbH, Schalksmuhle, Westphalia, Germany Filed Apr. 23, 1969, Ser. No. 818,604 Claims priority, application Germany, Apr. 25, 1968, P 17 63 252.9; Nov. 13, 1968, P 18 08 524.0 Int. Cl. H01h 71/14 US. Cl. 337-77 14 Claims ABSTRACT OF THE DISCLOSURE A switch unit in which a pair of contact means movable between an open and a closed position are arranged in a pair of chambers formed in a socket, in which an operating member cooperates with one of said contact means to move the same between the open and the closed position and with the other contact means to move the latter to the closed position, and in which heat-responsive means cooperate with the other of the contact means to move the latter from the closed to the open position when overload occurs in the circuit connected to the contact means. The unit may also include a signal lamp mounted on the operating member and the signal lamp may be connected to the contact means in such a manner that the lamp is energized either when the other contact means are in the open or when they are in the closed position.

BACKGROUND OF THE INVENTION The present invention relates to a switch unit, especially to a toggle switch unit constructed for side-by-side arrangement with other similar units and provided with heat-responsive means for opening a circuit connected to the switch unit when an overload occurs in the circuit. Known toggle switch units of the aforementioned kind are held when moved by an operating member to the closed position by the heat-responsive means and such switches use as contacts loosely insertable standard switch means, for instance microswitches operated by a spring which cooperates directly with the operating member or indirectly through the operating member with the heat-responsive means.

On the other hand, switch units, especially toggle switch units, are known in the art which comprise a socket formed by a pair of outer and one or a plurality of inner parts forming at least two chambers in each of which a movable contact member is arranged and in which the movable contact members cooperate with a common operating member.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a switch unit, especially a toggle switch unit, which comprises first and second contact means, each movable between a closed and an open position, and heat-responsive means cooperating with one of the contact means for moving the latter to the open position when an overload in a circuit connected to the contact means occurs.

It is a further object of the present invention to provide a switch unit of the aforementioned kind which is improved over switch units of this kind known in the art.

It is an additional object of the present invention to provide a switch unit of the aforementioned kind which is composed of relatively few and simple parts so that the switch unit may be manufactured at reasonable cost and will stand up perfectly after extended use.

With these objects in view, the switch unit according to the present invention mainly comprises a socket defining at least one pair of chambers, first and second contact means respectively mounted in the pair of chambers and each movable between an open and a closed position, operating means mounted on the socket means for moving the contact means from the open to the closed position, and heat responsive means cooperating with one of the contact means for moving the latter independent from the operating means to the open position when an overload occurs in a circuit connected to the contact means.

Preferably, the socket means comprises at least one central part and a pair of outer parts abutting and connected to the central part and constructed in such a manner to form with the latter the aforementioned pair of chambers in which the first contact means and the second contact means with the heat-responsive means cooperating therewith are respectively arranged. By providing more than one central part it is possible to enlarge the switch unit according to the present invention in any desired manner. Thus, by providing a plurality of abutting central parts, the switch unit may be constructed as a twopole or multipole switch in which one or a plurality of the contact means cooperate with heat-responsive means. The movable contacts may be arranged parallel to each other in the respective chambers and they may be electrically connected with each other to thus form any desired combination.

According to a further feature of the present invention, an indicating lamp may be provided on the operating member of the switch and cooperating with the first and second contact means in such a manner as to indicate the position of the contact means and especially to indicate when an overload occurs in the circuit connected to the switch. The signal lamp is preferably connected by means of contact springs to the first and second contact means.

According to a preferred arrangement of the present invention, the operating member cooperates with the first and second contact means in such a manner that in one position of the operating member the latter acts to open the first contact means and to close the second contact means, while in the other position of the operating member the first contact means are moved to the closed position while the second contact means are disengaged from the operating member so that they may open under the influence of the heat responsive means whenever an overload occurs. Preferably, the first contact means includes a rockable contact member tiltably mounted intermediate the ends thereof, and the second contact means preferably includes a rockable contact element extending substantially parallel and spaced from the rockable contact member and being mounted at one of the ends thereof movable between the open and the closed position. The rockable contact element cooperates with the heat-responsive means to be moved to the open position whenever an overload occurs in a circuit connected thereto.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal cross section through a first embodiment according to the present invention and showing the switch in open position;

FIG. 2 illustrates the contact means cooperating with the heat-responsive means, as shown in FIG. 1, but in FIG. 2. these elements are shown in the closed position,

whereas the socket means and the operating member are omitted in FIG. 2;

FIG. 3 is a top view of the switch unit shown in FIG. 1 with the operating member removed;

FIG. 4 is a partial longitudinal section through a second embodiment according to the present invention;

FIG. 5 is a longitudinal cross section through a third embodiment according to the present invention and illustrating the contact means cooperating with the heatresponsive element;

FIG. 6 is a longitudinal cross section through the same embodiment but this cross section is taken through the chamber in which the first contact means are located and showing these contact means in closed position; and

FIG. 7 is a top view of the embodiment illustrated in FIGS. 5 and 6 with the operating member removed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and more specifically to FIGS. 1 and 3 of the same, it will be seen that the switch unit according to the present invention may be constructed as a single pole toggle switch 4 comprising a socket 5 and an actuating member 6 mounted in the socket means 5 tiltable about a tilting axis .16. The actuating member 6 is substantially T-shaped and the centrally downwardly extending arm 7 cooperates with a rockable contact member 8 whereas a downwardly extending extension 9 at the right end, as viewed in FIG. 1, of the actuating member 6 cooperates with a movable contact member 10 of the thermoswitch 11. The rockable contact member 8 and the thermoswitch 1.1 are respectively arranged in two chambers 12 which are formed by the two outer parts 13 and the central part 14 of the socket 5. The central part 14 has a longitudinally extending separating wall 15 which separates the two chambers 12 from each other. The top edge of the separating wall 15 is located below the top edges of the two outer parts 13 and the pivot pin 16 of the actuating member extends, as clearly shown in FIG. 1, above the top edge of the separating wall 15 and is mounted at opposite ends in corresponding bores in the side walls of the outer members 13. The arm 7 is arranged laterally of the separating wall 15 to extend only into the chamber in which the rockable member 8 is located. The outer parts 13 are connected to the inner part 14 by rivets 117.

The movable contact member 8 is supported intermediate its ends on a narrow member 18 of conductive material for rocking movement and appropriate notches in the member 18 and in the movable contact member 8 prevent shifting of the latter in longitudinal direction. The right end, as viewed in FIG. 3, of the movable con tact member 8 carries a contact portion adapted to engage a stationary contact 19 at the bottom of the chamber 12 in which the movable contact 8 is located, when the latter is tilted in clockwise direction. The contact member .19 has a terminal portion, best shown in FIG. 1, which extends through the bottom wall of the socket 5 to be connected into an electric circuit in which the switch is to be used. A support member 20 for the movable contact member 10 of the thermoswitch 1 1 is located at the bottom of the other chamber 12 and held in place by a downwardly bent portion 21 engaging in a corresponding slot 22 formed in the bottom of this chamber and by an extension extending into a slot 23 formed in the right end wall, as viewed in FIG. 1, of the respective chamber. A bottom portion of the contact member 10 extends through a slot 25 of the support member 20 and shoulders 24 formed by opposite notches in the contact member 10 prevent longitudinal movement of this member relative to the support member 20. A tension spring 26 is connected at opposite ends to the contact member 10 and to an upwardly bent portion 27 of the support member 20 so as to yieldably hold the contact member 10 in the position as shown in FIG. 1. The members I18 and 20 are conductively connected through a web 28, as best shown in FIG. 3.

The contact member 10 is provided at its upper end with a bent portion 29 adapted to cooperate with the extension 9 of the actuating member 6 in such a manner that during tilting of the actuating member in clockwise direction about the axis 16, the contact member 10 is tilted in counterclockwise direction against the action of the spring 26 until the nose 30 of the contact member 10 is interlocked with a corresponding nose 35 on the free end of a bimetal strip 31, as shown in FIG. 2. The other end of the bimetal strip 31 is fixedly connected to a substantially U-shaped resilient support member 32 which in turn is connected by a threaded bushing 33 to the bottom wall of the socket 5. An adjusting screw 34 threaded into the bushing 33 engages with its upper end the upper arm of the U-shaped member 32 so that by adjusting the screw 34 the inclination of the bimetal strip 31 and therewith the position of the nose 35 at the end thereof in the cold condition of the bimetal strip may be slightly adjusted. A heating wire 36 is soldered at one end to the free end of the bimetal strip 31 and the other end of the heating wire 36 is connected to the other terminal 37 of the switch which extends through the bottom wall of the socket 5.

The above-described switch will operate as follows:

Assuming that at the start the bimetal strip 31 is interlocked with the movable contact member 10, as shown in FIG. 2, then tilting of the actuating member 6 in clockwise direction about its axis 16 will cause the movable contact member 8 to tilt likewise in clockwise direction so that its right end, as viewed in FIG. 3, will engage the stationary contact 19 whereby current may flow from the terminal 19 through the movable contact member 8, the conductive support member 18, the web 28, to the support member 20 and from there through the movable contact member 10, the bimetal strip 31 and the heating wire 36 to the other terminal 37. When now an overload occurs in the circuit to which the terminals 19 and 37 are connected, the bimetal strip 31 will bend so as to release the interlock between the noses 35 and 30, whereby the movable contact 10 will be moved under the influence of the spring 26- to the open position, as shown in FIG. 1, thereby interrupting the circuit. By tilting the actuating member 6 again in clockwise direction, the extension 9 on the actuating member will engage the bent portion 29 of the contact member 10 and move the latter against the force of the spring 26 to the position as shown in FIG. 2, and assuming the bimetal strip 31 has cooled off in the meantime, the interlock between the noses 30 and 35 will be restored. During this tilting of the actuating member the movable contact 8 will be tilted in counterclockwise direction thereby disengaging the right end of the movable contact member 8 from the stationary contact 19. Restoring the circuit will therefore require tilting of the actuating member 6 again in clockwise direction.

In the above-described arrangement, the actuating member slidingly engages the movable contacts. The arrangement is simple in construction and reliable in operation and the described switch may be easily expanded to a twopole or multi-pole switch with a single or a plurality of thermoswitches incorporated therein.

Instead of a tiltable actuating member 6-, as shown in FIG. 1, the switch may also be constructed with a longi tudinally moving actuating member. Such a construction is shown in FIG. 4, in which the switch unit is provided with a plurality of keys 39, only the front one of which is shown in FIG. 4, which are respectively connected to push rods 40 guided for movement in longitudinal direction in the socket 5. The push rods 40 are connected to each other and each of the push rods is provided intermediate its ends with a downwardly extending arm 7 cooperating with the tiltable contact 8 and with a downwardly extending extension 9 cooperating with the bent portion of the movable contact member 10 of the thermoswitch in the manner as described above in connection with the embodiment shown in FIGS. 1-3. Each of the push rods 40 is provided in the region of the left end thereof, as viewed in FIG. 4, with a cutout for a compression spring 42 which abuts with opposite ends thereof against an end wall of the socket 5 and the push rod 40, tending thereby to move the latter towards the left, as viewed in FIG. 4, Whereas the other ends of the push rods cooperate with a spring-loaded arresting rod 43. The arresting rod 43 is mounted in opposite ends on two plates 44 in direction transverse to the elongation of the push rods 40 and provided with bent portions 52 serving as arresting means. The upper open end of the socket 5 is closed by a cover 46. Otherwise, the switch unit shown in FIG. 4 is constructed in the same manner as described above in connection with FIGS. l-3.

The movable contact 8 is shown in FIG. 4 in the open position and when the key 39 is pressed inwardly, the movable contact 8 actuated by the arm 7 will snap to its closed position so that the circuit connected to the switch will be closed in the manner as described above in connection with FIGS. 1-3. In the inwardly pushed position of the push rods 40, the extension 9 will be spaced from the bent portion of the movable contact 10 so that in the event an overload occurs in the circuit, the noses 30 and 35 will become disengaged, whereupon the movable contact 19 will move under the influence of the spring connected thereto to its open position. The operation of the switch shown in FIG. 4 is therefore the same as described above in connection with FIGS. 13.

FIGS. 5-7 illustrate a third embodiment of a switch unit according to the present invention, The switch unit comprises again a socket 5 formed by a central part 14 and a pair of outer parts 13 connected to each other by rivets or the like in abutting relationship to form a pair of chambers 12 and 12' separated from each other by the longitudinal wall of the central member 14. A thermoswitch 1'1 is located in the chamber 12 and this thermoswitch comprises a bimetal strip 31 connected at its left end, as shown in FIG. 5, to a substantially V-shaped spring '68 which abuts with its lower leg against the bottom of the chamber 12 and is connected to this bottom in any convenient manner. The bent portion 69 of a rockable contact element 63- is likewise connected to the upper end of the spring 6 8. The element 63 extends longitudinally through the chamber 12 and the U-shaped bent opposite end of the element 63 carries at the bottom thereof a movable contact 72. The bent portion 70 is connected by means of a snapover spring 71 to the free end of the bimetal strip 31. A heating wire 36 wound about the bimetal strip is connected at one end thereof to the region of the free end of the latter and at the other end thereof to a terminal P extending through the bottom wall of the chamber 12. A stationary contact 73' is arranged opposite the movable contact 72 and connected to the bent portion 73 of the other terminal M which extends through the bottom wall of the chamber 12.

A two-armed rockable contact member 64 is arranged in the chamber 12' and tiltably mounted substantially midway between the ends thereof on the terminal P projecting substantially midway in the chamber 12' upwardly from the bottom wall and through the latter in downward direction beyond the socket 5. The rockable contact member 64 carries at its right end, as viewed in FIG. 6, a movable contact 74 cooperating with the stationary contact 73' mounted on the bent portion 73 of a terminal member M which extends through the bottom wall of the chamber 12'.

The actuating member 6' is mounted for tilting movement about a pin 67 which in turn extends over the central wall 15 and is journalled at opposite ends in corresponding bores of the side walls of the outer part 13 of the socket 5. A downwardly extending extension 65 in the region of the right end, as viewed in FIG. 5, of the actuating member 6 is adapted to engage, during tilting of the actuating member 6' in clockwise direction, the rockable contact element '63 so as to move the contact 72 con nected thereto downwardly into engagement with the stationary contact 73, whereby the spring 71 will snap over and hold the rockable contact element 63 in its closed position. An arm 66 integral with the actuating member 6' extends midway between opposite ends of the latter into the chamber 12. The arm 66 is formed with a central bore 76 in which a coil compression spring 77 is located which presses a ball 65 into engagement with the curved upper surface of the rockable contact member 64. In the position as shown in FIG. 6, the spring-pressed ball 65 engages the curved upper surface of the rockable contact member 64 to the right side, as viewed in FIG. 6, of the terminal P on the upper end of which the member 64 is tiltably mounted, to hold thereby the movable contact 74 in engagement with the stationary contact 73.

In the embodiment illustrated in FIGS. 5-7, the contact member 6 is provided with a cavity 58 in which a signal lamp 53 is located. The upper open end of the cavity is closed by a transparent insert 56 which engages with its lateral projecting noses 59 corresponding shoulders 60 formed by the cavity to thus hold the insert 56 in place. The signal lamp 53 has a pair of contact springs 54 and 54', portions of which are respectively located in diagonally opposite grooves 55 respectively formed in opposite end walls of the insert member 56 and the contact springs extend respectively over a portion 60 surrounding the pivot pin 67 of the actuating member 6' and respectively through openings 57 located to opposite sides of the portion 60 to engage with curved end portions 62 thereof the rockable contact element 63 and the rockable contact member 64, respectively.

The terminals P and P and M and M' are connected in circuit with a motor or similar electrical apparatus to be protected by the switch. In the position of the switch elements as shown in FIGS. 5 and 6, it is assumed that an overload occurred in the circuit, and due to the overload and corresponding heating of the bimetal strip 31 the thermoswitch 11 has been opened to the position as shown in FIG. 5. In this position current will flow from the terminal P through the heating Wire 36, the rockable contact element 63, the contact spring 54 engaging the element '63 through the lamp 53, the other contact spring 54' through the rockable contact member 64 and the contacts 74 and 73 to the terminal M, that is the lamp 53 will be energized and indicating thereby that an overload flows through the circuit connected to the terminals of the switch. When the operator now tilts the actuating member 6' in clockwise direction, the 'ball 65 engaging the curved upper surface of the rockable contact member 64 will slide on the surface to a point thereon located to the left, as viewed in FIG. 6, of the terminal P rocking thereby the contact member 64 in counterclockwise direction and disengaging the contacts 74 and 73' from each other, thereby interrupting the circuit connected to the terminals P and M. This tilting of the actuating member 6' will cause engagement of the extension 65 with the rockable contact element 63 to move the latter to a position in which the movable contact 72 will engage the stationary contact 73'. At the same time, the bent portion '62 of the contact springs 54 and 54' Will become disengaged from the element 63 and the member 64 so that the signal lamp 53 will be de-energized. By tilting then the actuating member 6 in counterclockwise direction to the position as shown in FIGS. 5 and 6, the contact member 64 will be tilted in clockwise direction to bring the contacts 74 and 73' again into engagement with each other while the contacts 72 and 73' of the thermoswitch 11 remain closed and the lamp 53 extinguished. Should an overload still exist in the circuit, the bimetal strip 31 will be heated and cause movement of the element 63 to the position as shown in FIG. 5 in which the lamp is again energized, indicating thereby that the overload still exists in the circuit.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of switch units differing from the types described above.

While the invention has been illustrated and described as embodied in a switch unit incorporating a heat-responsive element, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Thus, the signal lamp 53 could be connected in circuit with the other elements of the embodiment shown in FIGS. 7 in such a manner that the signal lamp is energized when the contact element 63 and the contact member 64 are in closed positions and de-energized when the contact element is in the position as shown in FIG. 5, or the elements of the thermoswitch may be replaced simply by a bimetal strip carrying at its free end a movable contact member. Likewise, an actuating member 6' with the signal lamp 53 and the contact springs 54 and 54' could be incorporated instead of the actuating member 6 in the embodiment shown in FIGS. 1-3.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. A switch unit comprising, in combination, a socket defining at least one pair of chambers; first and second contact means respectively mounted in said pair of chambers, each of said contact means being movable between an open and a closed position and each comprising a stationary contact and a movable contact member, the movable contact members being substantially parallel and electrically connected to each other; terminal means connected to said stationary contacts for connecting said contact means to an electric circuit; a single actuating member mounted on said socket means and having actuating portions extending into said chambers for moving said contact means from said open to said closed position; and heat-responsive means cooperating only with said second contact means for moving the latter indepedent from said actuating member to said open position when an overload occurs in said circuit.

2. An switch unit as defined in claim 1, wherein said socket means comprises at least one central part and a pair of outer parts abutting and connected to said central part and constructed in such a manner as to form with the latter said at least one pair of chambers.

3. A switch unit as defined in claim 1, wherein a plurality of first and second contact means are arranged sideby-side in a plurality of chambers.

4. A switch unit as defined in claim 1, and including a signal lamp on said actuating member in circuit with said first and second contact means.

5. A switch unit as defined in claim 4, wherein said signal lamp is connected in circuit with said first and second contact means to be energized when said second contact means is in said open position.

6. A switch unit as defined in claim 4, wherein said signal lamp is connected in circuit with said first and second contact means to be energized when said first and said second contact means are in said closed position.

7. A switch unit comprising, in combination, a socket defining at least one pair of chambers; first contact means comprising a stationary contact and a rockable contact member and second contact means, said contact means being respectively mounted in said pair of chambers, and each of said contact means being movable between an open and a closed position; terminal means for connecting said contact means to an electric circuit; operating means mounted on said socket means for moving said contact means from said open to said closed position; a signal lamp on said operating means; heat-responsive means cooperating with said second contact means for moving the latter independent from said operating means to said open position when an overload occurs in said circuit; and a pair of contact springs both connected at one end thereof to said lamp and one adapted to engage with the other end thereof said rockable contact member of said first contact means when the same is in said closed position, and the other adapted to engage said second contact means when the latter is moved by said heatresponsive means to its open position so that the lamp is energized when an overload occurs in said circuit.

8. A switch unit as defined in claim 7, wherein said second contact means comprises a stationary contact and a rockable contact element cooperating with said heatresponsive means, said other contact spring engaging said rockable element.

9. A switch unit as defined in claim 8, wherein said actuating means is movable between a first and a second position and cooperates with said rockable contact member of said first contact means and said rockable element of said second contact means to move in one of said end positions thereof said first contact means to said open and said second contact means to said closed position and in the other position thereof said first contact means to said closed position while permitting said second contact means to open under the influence of said heat-responsive means.

10. A switch unit as defined in claim 8, wherein said heat-responsive means comprises a bimetal strip connected by a snapover spring to said rockable contact element.

11. A switch unit as defined in claim 7, wherein said actuating means comprises a movable actuating member formed with a cavity having an upper open end, and including an insert member closing the open end of said cavity, said lamp being arranged in said cavity and said contact springs being in part' supported on opposite portions of said insert member.

12. A switch unit as defined in claim 11, wherein said actuating member is mounted on said socket means tiltable about a tilting axis located between opposite ends of said actuating member and wherein said contact springs extend with portions thereof respectively located to opposite sides of said tilting axis out of said cavity.

13. A switch unit as defined in claim 9, wherein two pairs of terminals are respectively coordinated with said rockable contact element and said rockable contact memher, one terminal of each pair being permanently connected to said contact element, respectively said contact member, and the other terminal of each pair carries in the respective chamber a stationary contact cooperating with a movable contact respectively provided on one end of said contact element, respectively said contact member.

14. A switch unit as defined in claim 13, wherein said stationary contacts are respectively fixed to portions of the other terminals which include with the remainder of the respective terminal an angle of substantially 90 and abut against the bottom of the respective chamber.

References Cited UNITED STATES PATENTS 2,438,186 3/1948 Randall 33766 2,483,646 10/1949 Kitman 337-52 2,922,004 1/1960 Miller 337 2,961,513 11/1960 Wood 33775 3,087,146 4/1963 Boudouris 337--56 3,108,165 10/1963 Cinibulk 337--66 HAROLD BROOME, Primary Examiner 

